Coupling light between an optical fiber or laser diode and a silicon photonic optical waveguide may be achieved using an edge coupler. An edge coupler can be fabricated on the silicon photonic chip, and can be used for efficient coupling in, for example, a butt-coupled configuration. One approach for designing an edge coupler device on a silicon photonic chip is a mode-converting edge coupler design. In such a design, a comparatively larger secondary waveguide is fabricated in close proximity to a comparatively smaller primary silicon waveguide. Here, light couples to the secondary waveguide from the optical fiber or the laser diode at an edge of the silicon photonic chip. The secondary waveguide may be designed such that an optical mode of the secondary waveguide matches that of the optical fiber or the laser diode. Light then adiabatically transfers from the optical mode of the secondary waveguide into an optical mode of the primary silicon waveguide. This transference can be brought about based on engineering one or more dimensions (e.g., a width) of the primary silicon waveguide (e.g., by reducing the width of the primary silicon waveguide nearer to an optical coupling facet of the secondary waveguide).